Scientific interest in neural networks, both computational and neurobiological, has exploded recently. To better understand the functional significance of multiple connections, neurobiologists need a system for routinely culturing neurons, especially mammalian central nervous system neurons, in patterns and in sufficiently low density that individual neurons and their contacts could be identified with the light microscope, individually stimulated electrically and have their action potentials individually recorded. This would permit the study of network and synaptic paradigms in vitro under conditions in which the chemical and electrical stimulus envirorunent can be controlled. The proposed work is to achieve this goal by combining existing techniques for electrode array fabrication and patterned, low density culture of central nervous system neurons. Two array/patterning systems will be investigated: 1. polyimide insulation with a neural substrate of polylysine selectively ablated by laser; 2. silicon dioxide insulation with patterns of covalently bonded areas of high (diamines) and low (alkanes) adhesion. An optimal electrode metal will be chosen from gold platinum, and iridium, possibly with an ultrathin layer of silicon dioxide. Also, a technique will be developed for preparing and examining by electron microscopy single contacts arising from low density cultures on planar surfaces. Last, electrical recording and stimulation of the geometrically patterned, low density cultures of hippocampal cells will be performed to determine efficacy of the technique.